In the utilization of single mode fibers for high bandwidth information transfer or for phase modulation applications, it is desirable to maintain the plane of polarization of polarized light or to force the polarization of unpolarized light. A single mode fiber with an elliptical core will maintain the plane of polarization of the injected light.
Low loss single mode optical fibers are preferably used in specified applications, for example in laser gyros; sonar detectors; interfacing elements, particularly interfacing optical fibers with integrated optic devices which use plane polarized light; and, particularly important, are high data rate communication systems.
It is well known in the field of optical fibers that single mode fibers are either required or desirable for the above listed applications and others. The problem to date has been to develop a method of fabricating a low loss single mode optical fiber which either maintains the polarized nature of polarized light or, by virtue of the geometry involved, will force the polarization of unpolarized light.
A number of workers in the field have published articles relating generally to the effect of ellipticity of the fiber core; have examined the magneto-optical properties of index-gradient optical fibers; have studied the delayed distortion in glass fiber optical waveguides due to small elliptical deformations of the cross-section; have studied the linear and circular birefringence properties of low loss single mode glass fibers which depend upon length; have studied the influence of a noncircular core on the polarization performance of single mode fibers; and have studied the polarization effects in short lengths of single mode fibers. References to the foregoing are found in the following publications:
1. Harms, H., Papp, A., and Kempter, "Magneto-optical Properties of Index Gradient Optical Fibers". App. Optics, 15, 3 pp 799-801, 1976.
2. Schlosser, W. O., "Delay Distortion of Weakly Guiding Optical Fibers Due to Elliptic Deformation of Boundary". B.S.T.J., 51, 2, pp 487-492, 1972.
3. Kapron, F. P., Borelli, N. F. and Keck, D. B. "Birefingence in Dielectric Optical Waveguides". IEEE Journal of Quantum Electronics QE-8, 2, pp 222-225, 1972.
4. Ramaswamy, V. and W. G. French, "Influence of Noncircular Core on the Polarization Performance of Single Mode Fibres", Electronics Letters, 14, 5, pp 143-144, 1978.
5. Ramaswamy, V., Standley, R. D., Sze, D., and French, W. G., "Polarization Effects in Short Length, Single Mode Fibers ", B.S.T.J. 57, 3, pp 635-651, 1978.
None of the above references teach an efficient, reproducible method of fabricating a low loss single mode polarizing optical fiber.